1. Field of the Invention
This invention relates to a method for manufacturing a semiconductor substrate that is generally used for a semiconductor device including a composite IC and an LSI.
2. Description of the Related Art
An SOI (Silicon On Insulator) semiconductor device has a semiconductor layer that is disposed on a semiconductor substrate through an intermediate insulating layer. Such an SOI substrate is suitably used for a device such as a composite IC, a high withstand voltage IC or an LSI for a portable instrument that is required to have high speed and low consumption power, in which several kinds of elements such as bipolar, MOS, and power elements are mounted on one chip.
To manufacture the SOI semiconductor device, an SOI substrate is required, which includes a high-quality crystalline semiconductor layer that is formed on a layer made of an insulating material such as SiO2 with extremely high resistance. Known conventional methods for manufacturing the SOI substrates include a bonding method, a SIMOX method, a method that combines bonding and ion implantation by utilizing hydrogen brittleness, and the like.
However, the SOI substrate manufactured by conventional techniques in any of the above-described methods is several to several dozen times more expensive than an ordinary bulk substrate. This is the biggest reason for preventing the SOI semiconductor device from being practically used, regardless of its inherent high performance and high functionality.